Our laboratory seeks to understand the process of messenger RNA decay in the model Gram-positive bacterium, Bacillus subtilis. While much is known about the mechanisms and regulation of transcription of DNA into mRNA and translation of mRNA into protein, relatively little is known about the intermediate step in gene expression - degradation of mRNA. Earlier work identified two major 3' exoribonucleases in B. subtilis, PNPase and RNase R, which can efficiently degrade mRNA decay intermediates subsequent to a decay-initiating endonuclease cleavage. More recently, two new classes of bacterial ribonucleases, the RNase J and RNase Y families, were discovered in B. subtilis. One of the B. subtilis RNase J enzymes, RNase J1, is a particular focus of interest as it specifies a 5'-to-3' exonuclease activity, an activity that is not present in more well-studied bacteria, such as E. col. The presence of a 5' exoribonuclease expands the scope of possible mechanisms by which mRNA can be degraded. New studies of RNase Y, an endonuclease, suggest that it plays a key role in determining the half-life of many mRNAs. This proposal applies the power of RNA-Seq (deep RNA sequencing) technology to explore mechanisms of mRNA decay at the transcriptome level. In particular, application of standard RNA-Seq to exoribonuclease mutant strains will be used to examine the role of 3' exonucleases, primarily PNPase and RNase R, in the turnover of mRNA decay intermediates. These studies will shed light on the question of ribonuclease redundancy, and whether specific ribonucleases act in the turnover of particular mRNAs. In addition, standard RNA-Seq will be used to study the role of RNase J1 5' exonuclease activity in the turnover of 3'-terminal fragments that contain the RNase-resistant transcription terminator structure. A modified RNA-Seq protocol called PARE (parallel analysis of RNA ends), which has been used by a number of laboratories to study eukaryotic mRNA processing, will be used to map 5'-monophosphate ends that arise in the course of mRNA decay. This protocol will be used to study the nature and distribution of cleavages by RNase Y, the major B. subtilis endonuclease, as well as by RNase III, a narrow-specificity endonuclease that is essential in B. subtilis. PARE will also be used to detect conversion of the native transcription product 5'-triphosphate end to a 5'- monophosphate end. This conversion may be a precursor step in the degradation of full-length mRNAs. RELEVANCE: Degradation of messenger RNA is an important step in regulating gene expression and is an essential function of bacteria. A thorough understanding of the mechanism of mRNA decay will enable design of antimicrobial agents that disrupt this process and thereby interfere with bacterial cell growth. PUBLIC HEALTH RELEVANCE: Messenger RNA (mRNA), the template molecule upon which proteins are synthesized, needs to be turned over rapidly to adapt to changing environments and to recycle the pool of ribonucleotides needed for new RNA synthesis. The mechanisms by which mRNA is degraded will be studied in detail in the model microorganism, Bacillus subtilis, using deep RNA sequencing technology that facilitates global views of RNA processes. Elucidating the mechanism of mRNA decay could lead to the design of antibiotics that inhibit this essential process and thereby prevent bacterial colonization of human tissues.